Refining of vegetable and animal oils



Patented June 30, 1953 JREFINI-NG F VEGETABLE ANIMAL OILS AND 'Douglas'W. Dron, Poughkeepsie, N. Y., and Frank A. Lindsey, J r'., Fredericksburg, Va., assignors'to The De Laval Separator Company, New York,

' N. Y.,a corporation of 'New Jersey No Drawing. Application November. 16, 1948, Serial N0. 60,398

Claims. (01. 260-425 This invention relates to the refining of vegetable'and animal oils, and more particularly to an improved process for refining such oils, especially expeller oils, from which removal of color bodies is desired.

While the invention may be used to advantage in the refiningof both vegetable and animal oils (or fats), it will be describedfor illustrative purposes in connection with the refining of crude vegetable oils-obtained" from seeds by expellers, as such oils present the greatest difiiculties with respect to decolorizing.

The 'use of conventional e'xpellers for obtaining crude vegetable oils from; seeds presents a serious problem in the subsequent refining operation. Mills utilizing expellers are generally operated at the maximum pressing capacity in order to obtain the maximum yield from the installation, and in some cases this has an adverse eifect upon the oil due to overheating. In such cases, the color becomes set in the oil and is difficult to remove. It is well known in the art to use lye for the purpose of removing color bodies from the oil. However, to the extent that lye has been effective for this purpose in prior processes, it has been accompanied by substantial refining losses.

An object of the present invention, therefore, is to overcome this difficulty in the refining of expeller and other oils.

A further object is to provide an improved process for refining vegetable and animal oils, which removes sufficient color to make the oil bleachable and at the same time maintains the refining losses at a minimum.

The invention may be utilized in connection with either soda ash or caustic soda refining processes, both types being well known in' the art. In the second or decolorizing stage of the refining process, according to the invention, a small amount of very strong lye is injected at low temperature into the oil, followed by agitation of the mixture to cause a thorough dispersion of the lye throughout the oil. The contact period for the lye and oil is sufficient to complete the reaction of the lye with the color bodies. Near the end of the contact period, water is added to dilute the lye, and the mixture is quickly heated to the optimum temperature for the centrifugal separation of the oil from the impurities.

In the preferred practice of the invention with the soda ash process, oil from the first stage of the process is treated by injecting into it, in the second or decolorizing stage, a small quantity of very strong lye at a temperatureof 70 to 80 F. The temperature of the oil into which the lye is injected should not be over F. We have found that good results are obtained by using lye of 45 to 50 B. in an amount within the range of 0.5 to 1.0% by volume of the oil. By using very strong cold lye, added to cold oil, the lye will attack the color bodies without .substantially 'af fecting the glycerides. Moreover, by .closely lim iting the amount of the lye, as described, "there will be practically no excess lye to act upon the glycerides and saponify some of the oil, after the lye action on the color bodies.

Following the lye injection, the cold mixture of lye and oil is severely agitated in a suitable mixing apparatus to cause the lye to be rapidly and thoroughly dispersed throughout the oil.

The duration of the severe agitation is dependent somewhat upon the ype of oil being treated, but as an example, violent agitation for a period of five minutes at a temperature of 80 F. produced excellent results in the treatment of one type of vegetable oil.

After the severe agitation, the moving stream of oil and lye is subjected to a less violent but continuous mixing for a period of from four to twenty minutes, to allow a contact time long enough to complete the reaction of the lye with the color bodies. During the final phase of this contact period, when the chemical action of the lye and the color bodies is substantially completed,'sufiicient water is added continuously to the mixture to dilute the lye to a strength of about 10 to 16 B. and at the same time the temperature is increased to approximately to F. A period of about two minutes is generally allowed for adding the water and bringing the oil and water up to the required temperature with sufiicient agitation to form a break in the emulsion, so that the mixture is ready for separation. The above-described dilution of the lye and rapid heating of the mixture causes a co- -'agulation of the color bodies and a small amount of soap, thereby expediting the subsequent separation, which may be effected in a conventional second-stage centrifugal separator.

tests on one type of vegetable oil, the optimum ranges were found to be:

0.5% of lye by volume to 3.0% of water by volume.

0.625% of lye by volume to 4.5% of water by volumei 035% of lye by volume to of Water 2. The improvement according to claim 1, in

volume.

soda method, in which case somewhat'morelye is used in order to neutralize the fatty acids andat the same time to remove the color. 7

It will be understood that the strength ofthe to the mixture commencing at a time when the mixture is still at said low temperature to dilute the lye, heating the mixture rapidly to the optimum temperature for centrifugal separation, and centrifuging :the V'mixture; to separate the oil from, the precipitated impurities and water.

which the addition of water and the heating are effected simultaneously.

-3.'The improvement according to claim 1, in

-WhiCh the lye, is added in an amount of about 0.5% toil.0-%';of"the oil by volume, at a strength of about 45 to'50 B.

lye, the amounts of the lye andwater which are added, and the contact time and temperatures, may be varied according to the characteristics of the oil under treatment. ever, the oil-is treated with strong cold lye at a low temperature, followed by v(1) severe agitation and a contact time adequate for complete reaction of the lye with the color bodies, (2) dilution by addition of water to obtain a relatively weak lye, (3) rapid heating to the optimum temperature for centrifugal separation (4) centrifuging the mixture to separate the oil from the impurities.

We claim:

1. In the process of refining vegetable and animal oils, the improvement which comprises adding a small quantity of strong, cold lye to the oil at low temperature, subjecting the mixture to violent agitation, maintaining the lye in thoroughly dispersed contact with the oil for a period sufficient to complete the reaction of the lye with the color bodies in the oil and at a low temperature of about 70 to 90 F., adding water In any case, how- 7 2G 4. The improvement according to claim 1, in

vwhich the addition of water and the heating are 4 effectedsimultaneously within a period of about two minutes.

5. The improvement according to claim 1, in which the lye is added in an amount of about 0.5% to 1.0% of the oil by volume, at a strength of about to B., and at a temperature of about to F., the addition of water and the heating being effected simultaneously within a period of about two minutes, the water being added in an amount sufficient to dilute the lye to a strength of about 10 to 16 B., and the mixture being heatedto a temperature of about to F.

' *DOUGLAS W. DRON.

FRANK A. LINDSEY, JR.

References Cited in the file of this patient 7 UNITED STATES PATENTS Number Name Date Clayton Dec. 10, 1946 

1. IN THE PROCESS OF REFINING VEGATABLE AND ANIMAL OILS, THE IMPROVEMENT WHICH COMPRISES ADDING A SMALL QUANTITY OF STRONG, COLD LYE TO THE OIL AT LOW TEMPERATURE, SUBJECTING THE MIXTURE TO VIOLENT AGITATION, MAINTAINING THE LYE IN THOROUGHLY DISPERSED CONTACT WITH THE OIL FOR A PERIOD SUFFICIENT TO COMPLETE THE REACTION OF THE LYE WITH THE COLOR BODIES IN THE OIL AND AT A LOW TEMPERATURE OF ABOUT 70* TO 90* F., ADDING WATER TO THE MIXTURE COMMENCING AT A TIME WHEN THE MIXTURE IS STILL AT SAID LOW TEMPERATURE TO DILUTE THE LYE, HEATING THE MIXTURE RAPIDLY TO THE OPTIMUM TEMPERATURE FOR CENTRIFUGAL SEPARATION, AND CENTRIFUGING THE MIXTURE TO SEPARATE THE OIL FROM THE PRECIPITATED IMPURITIES AND WATER. 